Frustrated Senate Republican leaders yesterday attempted a preemptive strike to end Sen. Gary Hart's (D-Colo.) crusade against the MX missile, as a key MX supporter in the House said the missile is in "very serious trouble" in that chamber.

Shortly before the Senate was to recess before a rare Saturday session, Armed Services Chairman John G. Tower (R-Tex.) unexpectedly brought up Hart's proposal to knock $4.6 billion in MX funds from a pending $200 billion defense authorization bill. In a procedural move aimed at demonstrating Hart's weakness, Tower then asked the Senate to reject the proposal in a test vote.

Hart, whose campaign for the presidential nomination has been languishing for lack of an eye-catching theme, had been holding off a vote in hopes of what he called "extended debate" on the issue. But Republicans wanted a test vote to demonstrate what Tower called the "futility" of Hart's anti-MX campaign, and Tower decided to force the issue just as the Senate was about to quit for the night.

Initially caught off guard and, as he put it, "a little embarrassed," Hart got a delay of the vote and later told reporters he would try today to turn Tower's maneuver into an exercise in futility. Hart said he and his supporters will join Tower in voting against the proposal, thereby rendering it meaningless as a test vote.

"All we want is a fair chance to debate the MX," Hart said, accusing the GOP leadership of an "erosion of the traditions of the Senate" in attempting such a maneuver.

Though odds favor eventual Senate approval of production funds for the land-based intercontinental missile, Rep. Les Aspin (D-Wis.), one of several prominent Democratic liberals who have supported the MX in the House, said "it looks as though it could go down" when that chamber votes on MX funding next week.

A bipartisan compromise on MX deployment--which led the House in May to approve flight-testing of the missile--has been "embraced so fervently" by President Reagan that it is "no longer perceived as a compromise," Aspin said at a breakfast meeting with reporters.

This not only threatens liberal support for $2.5 billion in MX production funds, he added in an interview, but jeopardizes conservative backing for other parts of the agreement, including arms control and planning for a smaller Midgetman missile that many MX critics favor.

As MX critics' fortunes looked up in the House, Hart's crusade against the missile in the Senate had trouble getting off the ground.

Unlike Tower's surprise move to force a vote, the closest Hart got to a confrontation on the Senate floor was a minuet-like dialogue with Tower in which Hart avoided saying when he would permit a vote on the MX, prompting Tower to suggest that Hart "would make Fred Astaire look like an amateur."

Tower also ridiculed Hart's refusal to call his anti-MX endeavors a filibuster, saying it reminded him of the euphemism employed by the late senator Everett M. Dirksen (R-Ill.): "attenuated educational dialogue."

Then, at a news conference, Minority Whip Ted Stevens (R-Alaska) dismissed Hart's efforts as "grandstanding for weekend publicity."

In the midst of it all came a testy exchange between Hart and Majority Leader Howard H. Baker Jr. (R-Tenn.) over Hart's suggestion that today's session, which many Democrats were planning to skip, be used for "serious discussion of serious issues" instead of roll-call votes.

"Could it be that senators might exchange views on issues, for once?" Hart asked.

Bristling at what he called "a tone of voice that is accusatory," Baker said he wasn't trying to "punish" Hart or anyone else by demanding votes today but rather was insisting the Senate accomplish something.

Aides said later that the Republican leadership, which called today's session after it became clear that Hart would talk at length about the MX, wanted to force a test vote to publicize Hart's lack of support.

Hart has conceded that he probably lacks the votes to delete the $4.6 billion for all MX-related activities from the pending $200 billion defense authorization bill, but said it is such an important issue that it should be discussed at length.

"If deployed, the MX missile would radically change our world . . . and risk the very future of civilization," Hart contended in opening the debate earlier this week.

On the same theme, Sen. Edward M. Kennedy (D-Mass.) said yesterday: "The MX is a dangerous and expensive first-strike weapon that will weaken deterrence and fuel the nuclear arms race, instead of advancing the cause of arms control . . . . The MX will not suddenly spur the Reagan administration to more flexible negotiating positions, nor will it lead to the eventual construction of Midgetman."

"If we get one major MX vote and if it's a big defeat for Hart , it's going to be hard to keep a filibuster going," a Republican aide said.

If the Senate debate goes past Tuesday or Wednesday, its vote could fall after the House vote. Baker and Tower have accused Hart of seeking to delay a Senate vote until after the House showdown, but Hart has denied such an intention, saying that the House vote is "irrelevant" to his cause.

Both Republican and Democratic strategists theorized that the timing could cut either way. Although a House vote against the MX might strengthen Hart's case among some waverers, it could increase pressure for a strong pro-MX stand by the Senate to achieve a balanced compromise in a House-Senate conference on the bill.